1. Technical Field
The present invention relates to occupant protection apparatuses in vehicles, such as automobiles.
2. Related Art
Japanese Unexamined Patent Application Publication Nos. H10-167000, 2000-142321, and 2011-152837 each disclose a pre-tension mechanism that retracts a strap, which extends across the front of an occupant sitting on a seat of an automobile, prior to or at the time of a collision. A pre-tension operation causes the back surface of the occupant sitting on the seat to be pressed against the backrest of the seat prior to the collision or at the time of the collision, so that when the occupant moves forward due to the collision, the posture of the occupant can be corrected. Thus, an impact load occurring at the time of the collision is readily applied to the occupant properly restrained by the strap, so that occupant protection performance can be achieved at the time of the collision.
However, in these existing pre-tension mechanisms, the pre-tension operation for retracting the strap commences prior to the collision or at the time of the collision, and the collision occurs in that state. Therefore, if the front of the vehicle sinks down due to, for example, a braking operation performed during the pre-tension operation, an area where the strap comes into contact with the occupant's body, such as the chest, receives a load occurring due to a change in the orientation of the vehicle in addition to a constraining pressure caused by the pre-tension operation for correcting the posture. In addition, when the collision subsequently occurs, an impact load occurring due to the collision is also applied. There is a high possibility that these three kinds of forces are added together and be applied to the contact area.